Ours: Blood Ties #3 by A. K. Rose

Secrets. Lies. Betrayal. I've done my fair share, risking everything to save her. My princess... My Ryth. Now we're cornered by those who run the Order. And we're at their mercy. Only one man can get us out. The man who knows the truth about this place... Her father. Deals are made to free us. Only she doesn't know everything. She soon will... She'll expect my brothers to be standing outside the gates.. Waiting... But I don't think they will. I'll be there to pick up the pieces. I'll make sure she's safe. Our little mouse. Our princess. Our... stepsister.